I'm open to investing in different regions of the country, and using that rental income to supplement renting personally in SD.

I look at my ROTH accounts as supplements to that, but I don't plan to withdraw my contributions any time soon. 

You must be prepared to supplement tenant's rent till you are ready to cash out.In your area investors develop very high risk tolerance and move forward hoping to get out before th emarkets change.

Could I use my LLC that the properties are in as a year's worth of income, supplemented with my current personal income?

Some questions I have are I have a new child, so I am not able to save much from my w2 job and looking to do a side hustle to supplement.

My goals are for now to supplement my income, but I want to be in a position in 5 years to be able to quit my day job and be a full time investor.

You can read their quarterly reports but they usually have even better information on their websites as 'supplements' to their earnings calls.

There is also the option of a 2nd mortgage (piggyback mortgage) to supplement your down payment, if you're not too far above the conforming loan limit. 

If anyone has questions on roofs I do residential and commercial roofs with multiple companies and specialize in understanding how to handle and supplement claims to get the most damage coverage possible.   

I am looking to supplement my primary income stream and expand into real estate investment.